In my U.S. Pat. No. 3,946,951 of Mar. 30, 1976, it was proposed to process difficult to defiber stock such as hemp, flax, rag, leather, synthetic fiber, wet strength paper and the like, in a vortical circulation pulper by reducing the clearance of the rotor/stator blades at the truncated conical attrition interface to zero and increasing the horsepower exerted on the zero clearance rotor at least fifty percent to achieve enough thrust and grinding action to refine the fibers. This operated successfully, but subjected the apparatus to wear at a rapid rate.
In my U.S. Pat. No. 4,365,761 of Dec. 28, 1982 entitled "Apparatus and Method for Defibering Unconventional Material" it is proposed that a rotor/stator stock reduction interface be provided in the path of the vortically circulated stock to reduce large chunks of the unconventional material to smaller pieces so that they may enter the stock attrition interface for defibering. The stator of the apparatus of my said application is symmetrical, and formed of a plurality of identical peaks and valleys which create acquisition valleys for retaining the chunks, each peak having an acquisition edge, so that the stock reduction edges on the rotor vanes will strike the chunks with a scissors-like series of impacts and thereby reduce the chunks to the desired size.
This apparatus and method has been unusually successful, but occasionally the stock reduction blades on the rotor and the stock reduction edges on the stator become worn and require "down time" for resharpening.